A penetrant inspection and magnetic-particle inspection inspect a deficiency, such as a crack (crack) having an opening in the surface of metal in a non-destructive manner. In the penetrant inspection, normally, a red liquid called penetrant is applied to the surface to be inspected, the penetrant is wiped out after a predetermined time passes, and white powder called a developer is applied. If there is a deficiency, such as a crack, the penetrant remaining in the crack comes to the surface due to capillary phenomenon, indicating a deficiency in red. In case of magnetic-particle inspection, a solution containing fluorescent magnetic powder is sprayed on a specimen or a magnetic substance to magnetize the specimen. If there is a deficiency, such as a crack, the magnetic flux is concentrated on the deficient portion, so that the fluorescent magnetic powder is gathered and emits green light when ultraviolet rays are irradiated, thereby showing a deficiency. Conventionally, those deficiency indications are observed visually to inspect deficiencies.
Such a visual inspection has a problem on the inspection reliability, such as missing of a deficiency due to the fatigue of an inspector or that different inspection results due to the difference in capability among inspectors are left merely by characters, such as “passed”.
With regard to the magnetic-particle inspection, an automatic inspection apparatus has been developed for those parts which are important and are to be mass-produced. As it is a special-purpose apparatus, it cannot easily inspect parts having multifarious shapes.
Further, as the penetrant inspection needs to detect surface colors as a two-dimensional distribution at high precision, even if there is a calorimeter capable of accurately measuring the chromaticity at a point, two-dimensional sweeping is needed. In terms of inspection time and cost, therefore, it is difficult to easily perform automatic inspection of parts having multifarious shapes.
Furthermore, when a specimen was large, there were cases where it could not tell what part of the specimen the image that was acquired by automatic inspection was or what part of the specimen the detected deficiency was.
Moreover, if both the penetrant inspection and magnetic-particle inspection can be done automatically by a single apparatus, the economical merit would be improved significantly, but such an apparatus and technology have not yet appeared so far.
It is therefore an object of the invention to provide a deficiency inspection method, a deficiency inspection apparatus and a deficiency-inspection aiding method which overcome the above-described problems and facilitate discrimination of real deficiencies.
It is also an object of the invention to provide a deficiency inspection method, a deficiency inspection apparatus and a deficiency-inspection aiding method which can easily find the position of a deficiency even on a large specimen.